
Bradford T. answered 10/20/23
Retired Engineer / Upper level math instructor
Use L(x)= f(a)+f'(a)(x-a)
Where f(x) = tan(x)
f'(x) = sec2(x)
L(x) = tan(a)+sec2(x)(x-a)
At a = 0
L(x) = 0 + (1)(x-0) = x
tan(x) ≈ L(x) = x
If you graph f(x) = tan(x) and g(x) = x, pick off all the intersections of f(x) and g(x).